Glucose may Contribute to Retrieval and Reconsolidation of Contextual Fear Memory Through Hippocampal Nr4a3 and Bdnf mRNA Expression and May Act Synergically with Adrenaline

Acetate enhances spatial memory in females via sex- and brain region-specific epigenetic and transcriptional remodeling

Metabolic control of chromatin and gene expression is emerging as a key, but largely unexplored aspect of gene regulation. In the brain, metabolic-epigenetic interactions can influence critical neuronal functions. Here, we use a combination of behavioral, proteomic and genomic approaches to demonstrate that the intermediary metabolite acetate enhances memory in a brain region- and sex-specific manner. We show that acetate facilitates the formation of dorsal hippocampus-dependent spatial memories in female but not in male mice, while having no effect on cortex-dependent non-spatial memories in either sex. Acetate-enhanced spatial memory is driven by increased acetylation of histone variant H2A.Z, and upregulation of genes implicated in spatial learning in the dorsal hippocampus of female mice. In line with the sex-specific behavioral outcomes, the effect of acetate on dorsal hippocampal histone modifications and gene expression shows marked differences between the sexes during critical windows of memory formation (consolidation and recall). Overall, our findings elucidate a novel role for acetate, a ubiquitous and abundant metabolite, in regulating dorsal hippocampal chromatin, gene expression and learning, and outline acetate exposure as a promising new approach to enhance memory formation.

Molecular pathways underlying sympathetic autonomic overshooting leading to fear and traumatic memories: looking for alternative therapeutic options for post-traumatic stress disorder

The sympathoadrenal medullary system and the hypothalamic-pituitary-adrenal axis are both activated upon stressful events. The release of catecholamines, such as dopamine, norepinephrine (NE), and epinephrine (EPI), from sympathetic autonomic nerves participate in the adaptive responses to acute stress. Most theories suggest that activation of peripheral β-adrenoceptors (β-ARs) mediates catecholamines-induced memory enhancement. These include direct activation of β-ARs in the vagus nerve, as well as indirect responses to catecholamine-induced glucose changes in the brain. Excessive sympathetic activity is deeply associated with memories experienced during strong emotional stressful conditions, with catecholamines playing relevant roles in fear and traumatic memories consolidation. Recent findings suggest that EPI is implicated in fear and traumatic contextual memories associated with post-traumatic stress disorder (PTSD) by increasing hippocampal gene transcription (e.g., Nr4a) downstream to cAMP response-element protein activation (CREB). Herein, we reviewed the literature focusing on the molecular mechanisms underlying the pathophysiology of memories associated with fear and traumatic experiences to pave new avenues for the treatment of stress and anxiety conditions, such as PTSD.